Which of these knives are better for everyday use, and which is better for defensive use? Also, is it better to get one in a plain blade, or the black coating? Or is there another knife(in this price range)that I should know about?

I have both. I find the tanto blade isn't very useful as a work knife, but it is good for stabbing/puncturing, and it doesn't go over very well at the airport (I have teh combo blade on it. The AFCK is a great all-around knife both for utility and self-defense, doesn't seem to raise much attention (plain blade) at the security ckpt. The black coating is nice. Go for it. M2

The AFCK is a better all around carry knife. The plain edge blade is good but the partially serrated models have the best of both worlds. If you really need to get the BT blade, you may want to go ahead and buy the M2 (toolsteel) AFCK. I don't have one in M2 but what I understand is that they are tougher and hold an edge even better than the ATS 34 models. The Axis Lock may also suit your needs, it is very similar (size wise) to the AFCK, and has what some consider a better lock mechanism.
Another thing to consider about the BT (black) blade is where you live and what your uses will be. The black blades look nice until you really start using the knife and the BT starts wearing off. If you are in a humid climate and not able to take care of your knives with reasonable frequency, the BT would be a good investment.
Others to consider:
Spyderco Military
Spyderco Starmate
Emerson Raven (clip or tanto)
Emerson Commander (my favorite)
REKAT Carnivour
Outdoor Edge Impulse (budget knife)

Phillip hit the nail on the head.
The AFCK is a much better knife if you have to pick one or the other. I dont have any use for a tanto like point anyway. The Mini AFCK is also very good.
I have both... I carry my mini more often because the full size AFCK is a very large pocket knife and tends to frighten the sheople.
I have sent my favorite Mini AFCK off to a custom knife maker for some modifications. I am having the black G-10 replaced with blue anodized Ti scales and a contoured clip . Why? I dont know - Will look better with my suit - maybe.

------------------"A fear of weapons is a sign of retarded sexual and emotional maturity." - Sigmund Freud RAGE AGAINST THE MACHINE

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